A 10-year-old in Mumbai walks home from school through a waterlogged lane, with dirty rainwater reaching his ankles. The water has mixed with runoff from an overflowing drain.
For the next two weeks, he seems perfectly fine.
Then comes a fever, followed by body ache and a headache. His parents assume it is one of the viral infections that often go around during the monsoon.
When the fever refuses to settle, a doctor asks them one important question: Did he walk or play in dirty rainwater recently?
That small detail can completely change what the doctor looks for.
During Mumbai’s monsoon, doctors are watching closely for leptospirosis, a bacterial infection that people can pick up after coming into contact with water contaminated by the urine of infected rats, cattle or dogs.
For parents, the tricky part is that a child may fall sick several days after playing in puddles or walking through a waterlogged street. By then, the rainwater they came into contact with may be the last thing anyone remembers.
Dr Amol Jaybhaye, Consultant in Infectious Diseases at Narayana Health SRCC Children’s Hospital, says Mumbai has already seen more leptospirosis cases this year compared with the same period in previous years.
Children can be particularly vulnerable because they are more likely to splash through puddles, play in stagnant water or walk barefoot during the rains.
The Brihanmumbai Municipal Corporation’s Epidemiology Cell data also shows why doctors take the infection seriously.
Among suspected deaths linked to monsoon illnesses that were reviewed in 2025, leptospirosis had the highest confirmation rate. About 59.4% of suspected leptospirosis deaths were confirmed after clinical review, a higher proportion than malaria and dengue.
The fever can show up days after the rain
One reason leptospirosis can be difficult to spot early is the gap between coming into contact with contaminated water and actually feeling unwell.
According to Dr Jaybhaye, symptoms usually begin two to 14 daysafter contact, although they can sometimes take as long as 30 days to appear.
This means a child could walk through a flooded street, return to school and go about their routine for days before suddenly developing fever, chills, muscle pain or a headache.
These symptoms can easily look like a regular viral fever.
The bacteria can enter the body through even a tiny cut or scratch on the skin. They can also enter through areas such as the eyes, nose or mouth. This makes children playing barefoot around dirty or stagnant rainwater more vulnerable.
In many cases, early treatment can control the infection. If treatment is delayed and the illness becomes severe, however, it can begin affecting major organs.
Symptoms can appear 2 to 14 days after contact with dirty rainwater. Photograph: (Hindustan Times)
The United States Centers for Disease Control and Prevention says untreated leptospirosis can damage the kidneys, cause meningitis, affect the liver and lead to breathing problems. Severe cases can also become life-threatening.
Parents should seek medical attention promptly if a child who has recently been around dirty rainwater develops a persistent high fever, breathing difficulty, yellowing of the eyes or skin, or starts passing much less urine than usual.
These signs may suggest that the infection is beginning to affect vital organs.
Mumbai’s civic authorities have also increased their focus on monsoon illnesses this year.
Comparative data from January to July 2026 shows a rise in malaria, dengue and leptospirosis cases across the city.
The BMC has advised people who have walked through stagnant rainwater or mud while having cuts or scratches on their skin to speak to a doctor. Depending on the situation, a doctor may recommend preventive antibiotics within 24 to 72 hours of contact.
The civic body has also increased inspections at construction sites where water can collect and expanded fogging drives across residential wards as part of its wider monsoon response.
When to take your child to a doctor
There is some reassurance for parents: leptospirosis usually responds well to antibiotics when doctors identify and treat it early.
Dr Jaybhaye, however, advises parents against buying antibiotics over the counter and giving them to children on their own.
The right medicine, dose and duration depend on a proper medical assessment. A doctor also needs to understand the child’s symptoms and recent history before deciding on treatment.
The best protection begins with reducing contact with dirty rainwater wherever possible.
During heavy rains, parents can encourage children to stay away from puddles and waterlogged lanes and choose indoor play when streets are flooded.
Any cuts or scratches should be covered with waterproof dressings before a child steps outside.
If contact with rainwater cannot be avoided, children should wash their feet properly afterwards and dry them carefully, including the spaces between their toes.
Even a small cut can let bacteria enter after contact with dirty rainwater. Photograph: (TNIE)
Doctors also recommend drinking boiled or filtered water and keeping rats under control around the home, since rat urine is a major source of infection in cities.
And there is one simple habit parents can carry through the monsoon: remember where your child has been.
If your child develops a fever days or even weeks after walking or playing in dirty rainwater, mention it to the doctor.
The connection may seem small, especially once the roads have dried and the rain has moved on. For a doctor trying to understand why a child is ill, that detail can be extremely useful.
It can help them consider leptospirosis early, begin the right treatment and prevent an infection that responds well to timely antibiotics from becoming serious.
